This proposal aims to understand the role that short-term synaptic dynamics, such as depression and facilitation, play in the generation and coordination of oscillations in the nervous system. Synaptic interactions are key to the generation of temporal dynamics and are present in all synapses, but only recently have been studied in the context of generation and patterning of oscillations. In an oscillatory network, such short-term dynamics provide a mechanism that allows synapses to adjust their strength as a function of frequency;the synapses, in turn, shape the output of the network. This recursive relationship underlies the formidable complexity of these networks. Small neuronal networks are amenable to studying such complexities. We investigate the cellular and synaptic mechanisms underlying oscillations in the crustacean pyloric network, a model system for studying rhythmic motor pattern generation. Using a combination of electrophysiology and computational modeling techniques, we examine how distinct mechanisms of synaptic release interact to produce synaptic output. Our aim is to understand how the effects of frequency on synaptic strength give rise to new emergent network properties. There is overwhelming evidence that network activity is shaped not only by synaptic dynamics, but also by extrinsic neuromodulation, enabling networks to produce multiple functional outputs. Furthermore, synaptic dynamics are also altered by neuromodulators, thus leading to new patterns of network activity. We explore how neuromodulation affects short-term synaptic dynamics and how these effects reshape the network output. Characterizing the effects of neuromodulatory substances on synaptic dynamics may elucidate the actions of these substances in generating network oscillations such as during transitions between sleep and arousal states. Model networks in invertebrates have been used for decades to extract principles that were later shown to apply in mammalian networks. General principles obtained from studying the functions of synaptic dynamics in the generation and coordination of pyloric oscillations may potentially apply to other oscillatory networks that show activity-dependent changes in synaptic efficacy. Understanding these cellular and synaptic mechanisms provides important insight into the generation of self-organized oscillations of the brain, such as the multiple rhythms observed during sleep cycles or in structures involved in learning and memory formation and often affected in pathological conditions including epilepsy, depression and schizophrenia.